ENVIRONMENTAL EXPOSURE TO CROCIDOLITE AND MESOTHELIOMA - EXPOSURE-RESPONSE RELATIONSHIPS

This study aimed to estimate exposure-response relationships for mesot helioma and environmental exposure to crocidolite. Al 4,659 former res idents of Wittenoom, Western Australia (WA) who lived there between 19 43 and 1993 for at least 1 mo and were not directly employed in the cr ocidolite industry, were followed-up through the WA death, cancer and mesothelioma registries, electoral rolls, and telephone books. In 1992 , all subjects who should be traced were sent a questionnaire. Exposur e levels were estimated from results of periodic environmental surveys and duration of residence. Incidence rates were standardized to the W orld Population and Cox Regression was used to estimate the effects of exposure on incidence. To the end of 1993, 27 cases of mesothelioma w ere diagnosed. Mesothelioma cases stayed longer at Wittenoom, had a hi gher average intensity of exposure, and a higher cumulative exposure t o crocidolite than control subjects. The standardized incidence of mes othelioma was 260 per million person-years, and was similar for males and females. The rate increased significantly with time from first exp osure, duration of exposure and cumulative exposure. At these levers o f crocidolite exposure, there is a significantly increased risk of mes othelioma, which is dose-dependent.